Efferent function can be measured non-invasively by the study of contralateral effects on otoacoustic emissions. We propose to study the development of efferent effects on hair cell emissions in gerbils, mice and guinea pigs, and to pursue a provocative finding made during this period's research: infants of 24-28 week gestational age appear to have a persistent year-long post-natal lengthening of C.A.P. latency which is unrelated to conductive hearing loss. Therefore we will study the development of contralateral stimulation effects on Wave I of the ABR as well as hair cell emissions of premature and term infants. Contralateral suppression of emissions is a small but powerful physiological measure of efferent function. We have found in our practice a set of patients who show no suppression of hair cell function under contralateral stimulation but who, at the same time, show enormous emissions along with absent ABR's and MLR's as well as very poor speech discrimination. Dr. Arnold Starr has recently reported on similar patients who have normal pure tone audiograms but absent ABR's. We propose to collaborate with Starr to study 10 of these unusual patients culled from our joint practices. Finally, parents of Usher Syndrome Type I patients are obligate carriers of the gene for the disease. In conjunction with Dr. Keats, who is searching for the gene for this disease in Project II, we will test the hypothesis that abnormalities in hair cell emission suppression patterns might predict the presence of the gene.